给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

    示例 1：
    输入：n = 3
    输出：[[1,2,3],[8,9,4],[7,6,5]]

    示例 2：
    输入：n = 1
    输出：[[1]]

    提示：
    1 <= n <= 20

    1. class Solution:
    2.     def generateMatrix(self, n: int) -> List[List[int]]:   
    3.         matrix = [[1] * n for _ in range(n)]
    4.         flag = [[False] * n for _ in range(n)]
    5.         value = 1
    6.         x, y = 0, 0
    7.         while True:
    8.             while flag[x][y] is False:    # 向右打印
    9.                 matrix[x][y] = value
    10.                 if value == n ** 2:
    11.                     return(matrix)
    12.                 value += 1
    13.                 flag[x][y] = True
    14.                 if y == n - 1:
    15.                     x += 1
    16.                     break
    17.                 else:
    18.                     if flag[x][y + 1] is False:
    19.                         y += 1
    20.                     elif flag[x + 1][y] is False:
    21.                         x += 1
    22.                         break
    23.                     else:
    24.                         break
    25.             while flag[x][y] is False:    # 向下打印
    26.                 matrix[x][y] = value
    27.                 if value == n ** 2:
    28.                     return(matrix)
    29.                 value += 1
    30.                 flag[x][y] = True
    31.                 if x == n - 1:
    32.                     y -= 1
    33.                     break
    34.                 else:
    35.                     if flag[x + 1][y] is False:
    36.                         x += 1
    37.                     elif flag[x][y - 1] is False:
    38.                         y -= 1
    39.                         break
    40.                     else:
    41.                         break
    42.             while flag[x][y] is False:    # 向左打印
    43.                 matrix[x][y] = value
    44.                 if value == n ** 2:
    45.                     return(matrix)
    46.                 value += 1
    47.                 flag[x][y] = True
    48.                 if y == 0:
    49.                     x -= 1
    50.                     break
    51.                 else:
    52.                     if flag[x][y - 1] is False:
    53.                         y -= 1
    54.                     elif flag[x - 1][y] is False:
    55.                         x -= 1
    56.                         break
    57.                     else:
    58.                         break
    59.             while flag[x][y] is False:    # 向上打印
    60.                 matrix[x][y] = value
    61.                 if value == n ** 2:
    62.                     return(matrix)
    63.                 value += 1
    64.                 flag[x][y] = True
    65.                 if x == 0:
    66.                     y += 1
    67.                     break
    68.                 else:
    69.                     if flag[x - 1][y] is False:
    70.                         x -= 1
    71.                     elif flag[x][y + 1] is False:
    72.                         y += 1
    73.                         break
    74.                     else:
    75.                         break
    1. class Solution:
    2.     def generateMatrix(self, n: int) -> List[List[int]]:
    3.         l, r, t, b = 0, n - 1, 0, n - 1
    4.         mat = [[0 for _ in range(n)] for _ in range(n)]
    5.         num, tar = 1, n * n
    6.         while num <= tar:
    7.             for i in range(l, r + 1): # left to right
    8.                 mat[t][i] = num
    9.                 num += 1
    10.             t += 1
    11.             for i in range(t, b + 1): # top to bottom
    12.                 mat[i][r] = num
    13.                 num += 1
    14.             r -= 1
    15.             for i in range(r, l - 1, -1): # right to left
    16.                 mat[b][i] = num
    17.                 num += 1
    18.             b -= 1
    19.             for i in range(b, t - 1, -1): # bottom to top
    20.                 mat[i][l] = num
    21.                 num += 1
    22.             l += 1
    23.         return mat